1. Field of the Invention
This invention relates to a mechanized power assisted apparatus for applying tanned hides on a smooth flat plate preparatory to drying in the course of leather manufacture.
Tanning of leather is an ancient art. From the earliest times, man has changed rough raw animal hides into supple wearable materials. This involves mechanical and chemical treatment of the hide to remove blood, lymph, adhering flesh, hair, etc. and enzymatic and bacterial action to render the hide soft and supple. These are wet treatments. The leather is commonly dyed and treated with oils and fats for lubrication, softness, strength and water-proofing. After dyeing and fat-liquoring, leather contains about 45 to 60 per cent water and is commonly dried to about 14 percent moisture. Chemical and physical reactions take place during drying. Loose tannins, dyes and oils spread uniformly, penetrate deeply and are firmly fixed. Uneven drying causes migration of unfixed tannin, dye and oil to the surface, resulting in undesirable dark stains and non- uniform appearance.
A common industry technique of drying wet hides has been so-called "paste drying." Hides are literally pasted by the grain side to large flat plates of adhesive coated glass, porcelain or metal, and then are passed through a tunnel dryer. After drying to the desired moisture content, the hide is stripped off yielding flat, smooth grain, large area leather sheets ready for finishing and fabricating into various leather goods. Alternatively, the wet hides may be vacuum dried after being similarly spread out on a flat smooth polished plate.
Whether to be paste dried or vacuum dried, it is essential that the wet hide be in intimate contact with the smooth planar surface without any entrapped air bubbles. The wet hide is applied to the surface and manually smoothed by means of a squeegee-type slicker element. This is most commonly in the form of a flat edged blade which is manipulated over the surface of the wet hide from the center to the edge working out any entrapped air or water between the hide and plate surfaces. At the same time, the hide is stretched somewhat increasing its area. This is tough, arduous work requiring great strength and staying power. Typically, in the course of a day's work, fatigue sets in toward the end of the day and productivity is materially reduced.
Vacuum drying is faster, requires costly equipment and is somewhat less productive. Vacuum driers utilize flat horizontal beds. To slick the hide the operator must reach in from the edge of the bed. It is difficult to exert force on the hide when the slicker is held at arm's length. Because of this the hide is less uniform and is not stretched as much, compared to use of a vertical plate all areas of which may be closely approached. In spite of the somewhat reduced yield in hide area, the industry trend is toward greater and greater use of horizontal bed vacuum driers. The principal objective of the present invention is to provide a mechanical power assisted apparatus to perform the back-breaking task of slicking hides on a horizontal bed, with its attendant advantages of lessened fatigue, higher productivity, and more uniform product, overcoming the disadvantages of current vacuum drying practices.
2. The Prior Art
U.S. Pat. No. 4,596,124, issued June 24, 1986, discloses a power assist hide applicator apparatus for flattening and stretching a wet hide against a smooth vertical planar surface for drying. The apparatus is adapted for positioning closely adjacent to the smooth flat vertical plate upon which a hide is adhered for drying according to conventional tanning practice. The apparatus comprises support means holding a slicker element for positioning closely adjacent to a hide-carrying plate. The slicker element has a smooth flat edge which is rotatable in a plane parallel to the surface of the plate. The slicker element support means is associated with a power assisted travel means for moving the support means in a plane parallel to and spaced from the surface of the hide-carrying plate and over an area substantially coextensive with the area of a hide supported on that plate. Power assisted thrust means are associated with the slicker element for moving the element on a horizontal path perpendicular to the vertical hide-carrying plate into and out of contact with a wet hide carried on the plate and for exerting force on the slicker element. Spaced apart manually operable control means are disclosed for actuating the power assist means for manipulating the slicker element over the vertical surface of a hide in simulation of manual hide application.